Disease and damage at the level of the Descemet's membrane/corneal endothelium complex may result in production of retrocorneal fibrous membrane (RCFM). This pathological membrane residing posterior to Descemet's membrane is composed of irregularly arranged collagen fibrils and fibroblast-like cells that are endothelial in origin. This is a final pathway for a number of corneal disease processes that result in loss of function of the corneal endothelium, corneal edema, and progressive corneal opacity and scar. Such corneal scarring remains a leading cause of blindness in this county and the world. Yet we are not able to explain the mechanisms of retrocorneal fibrous membrane production. We have studied collagen phenotypes in normal rabbit corneal endothelial cells and in the experimentally produced RCFM in rabbit eyes. Biochemical studies have indicated an apparent change in collagen phenotype in RCFM. Ultrastructural studies also indicate that fibroblast-like cells in RCFM have characteristics of endothelial cells and of fibroblasts. We have hypothesized that polymorphonuclear leukocytes (PMNs) that are involved in the earliest stages of inflammation will damage basic components of the endothelial cells and the supporting connective tissues by release of enzymes. This subsequently alters cell-cell interactions and cell-extracellular matrix interactions. Thus endothelial cells may become modulated and eventually transformed in vivo. Therefore, the role of polymorphonuclear leukocytes on endothelial cells in culture and in vivo will be determined. The process of endothelial modulation caused by PMNs will be documented at the level of expression of collagen phenotype in addition to morphological changes. Collagen phenotype will be determined by incorporation of radioactive precursors, purification (sedimentation, chromatogrphy), SDS electrophoresis, and CNBr peptide maps. In addition, transition of the process in the individual cells will be studied with immunofluorescence. Understanding the mechanisms of transformation of endothelial cells may provide avenues of therapy and prevention of corneal diseases at the level of Descemet's membrane/endothelium complex.